Abstract: Geometries and energies of various low-energy conformers of the stereoisomers of 2,2,4, 4-tetrachloropentane and 2,2,4,4,6,6-hexachloroheptane were determined at the MP2 level with a 6-311++G** basis set. For 2,2,4, 4-tetrachloropentane, the energy of the conformer with gauche-gauche arrangement is lower; For 2,2,4,4,6,6-hexachloroheptane, the conformer with trans-gauche-trans-gauche arrangement is stable. In contrast, the conformer with trans-trans arrangement is unstable and the energy is higher. Based on the quantum calculations, the first- and second-order characteristic interaction can be obtained by comparing the energies among different conformers of the stereoisomers which are used to determine the statistical weight parameters in a rotational isomeric state model. According to the geometries of the conformers and the statistical weight parameters, we can construct six-state statistical weight matrices. Furthermore, the populations of CH₂ and CCl₂ centered dihedral pairs in poly(vinylidene chloride) are determined from the quantum chemistry based rotational isomeric state model.

Key words: Ab initio calculation, Poly(vinylidene chloride), Conformational distribution